The present invention is a magnetic recording head for recording information to a storage medium. In particular, the present invention is a magnetic recording head which employs a last insulator layer for the purpose of providing a proper take-off angle.
Presently there are two types of recording heads used in a computer device. First, there is an inductive magnetic recording head which incorporates an inductive writer portion and an inductive reader portion. Second, there is a magnetoresistive recording head which incorporates an inductive writer portion and a magnetoresistive reader portion. Thus, regardless of the type of reader portion which is utilized in the recording head, the writer portion is an inductive writer portion.
A typical inductive writer of a recording head consist of one or more coil conductor layers protected by insulating layers and surrounded by upper and lower magnetic cores (also called top and bottom poles) which are separated at the air bearing surface by a thin magnetic gap layer. Fabrication of the coil layers typically involves planarizing the surface on which the coils will be positioned with either a photoresist process or a metallic layer and photoresist combination process. Individual coils are then positioned on the planarized surface and encapsulated with another photoresist layer to insulate and electrically isolate the coil as well as protect the coils from damage during subsequent processing steps.
As coils are typically stack several layers high, most insulating photoresist layers provide insulation and isolation of a coil layer and provide a planarized top surface upon which a succeeding coil layer in the stack can be fabricated. Coil layers will typically form stepped surfaces in which the next coil layer is either larger than the previous coil layer, when coil layers are formed upon a recess bottom pole, or is smaller than the preceding layer, when coil layers are formed on a planarized bottom pole or extend above the recess portion of the bottom pole.
There are two critical dimensions of an inductive writer portion of a recording head which are determined by the location, placement and topography of the coil insulating layers. These dimensions are the takeoff angle (TOA) and the zero throat position. The TOA is defined as the angle between the upper and lower magnetic cores at the point where the magnetic cores separate from one another to surround coil layers and photoresist layers. The zero throat position is defined as the distance between either the separation point of the upper and lower magnetic cores and the point at which a recess begins for a recessed bottom pole, or between the separation point of the upper and lower magnetic cores and the location of the second to last insulating layer for a planarized bottom pole.
In a typical inductive writer, the TOA and zero throat position are determined by the position and thickness of the photoresist layer used to insulate and electrically isolate the last coil layer. Thus, the photoresist which determines the zero throat position and the TOA is also used to protect and insulate a coil layer, i.e. the last fabricated coil layer. This use restricts the thickness of the photoresist to a narrow range as well as restricts the range of available zero throat positions.
The efficiency of an inductive writer is determined in part by the TOA, as this angle influences how much flux can leak from the upper magnetic core to the lower magnetic core without crossing the gap oxide layer at the air bearing surface. Head efficiency and performance is also influenced by the throat height, which is the distance between the air bearing surface and the zero throat position. The throat height is determined by the zero throat position and by how far the head is lapped from the air bearing surface during fabrication. The zero throat position can also interact with the TOA in that the TOA is increased the closer the zero throat position is located towards the coil stack.
There is a need for a writer portion of a magnetic recording head and a method of making a writer portion of a magnetic recording head which accurately controls the take off angle and the zero throat position of the writer. The TOA influences how much flux can leak from the upper magnetic core to the lower magnetic core without crossing the gap oxide layer as well as pinches or limits the amount of transferable flux during a writing process. In addition, control of the take off angle is crucial for subsequent wafer process use, most notably the forming of the pole pieces for track width control. In addition, depending on the type of material used for the top pole, the physical properties of the top pole can be influenced by the take off angle.